Author Topic: New tubeless convert... or so I thought  (Read 11203 times)

dim

“No great mind has ever existed without a touch of madness.” - Aristotle

zigzag

  • unfuckwithable
Re: New tubeless convert... or so I thought
« Reply #76 on: 01 November, 2017, 07:38:18 am »
http://www.cyclingweekly.com/videos/cycling-tech/tubeless-tyres-tested-destruction
this test only tells half a story, pin and nail holes are easiest to seal and they are rarely a cause for punctures in real world. cuts by small shards of glass and flints that damage the casing are most tricky to seal. inner tubes and tyre boots still need to be carried for random incidents, e.g. screw making a hole in both tyre and rim.

Re: New tubeless convert... or so I thought
« Reply #77 on: 01 November, 2017, 10:05:06 am »
http://www.cyclingweekly.com/videos/cycling-tech/tubeless-tyres-tested-destruction
this test only tells half a story, pin and nail holes are easiest to seal and they are rarely a cause for punctures in real world. cuts by small shards of glass and flints that damage the casing are most tricky to seal. inner tubes and tyre boots still need to be carried for random incidents, e.g. screw making a hole in both tyre and rim.



I reckon someone snuck up with a powerdriver in hand to put that one there

citoyen

  • Occasionally rides a bike
Re: New tubeless convert... or so I thought
« Reply #78 on: 01 November, 2017, 12:03:06 pm »
Regarding the fitting of tubeless tyres, they really ought be harder to fit than regular clinchers for all the reasons Brucey mentions. That much makes perfect sense to me.

I didn't find it especially hard fitting my Schwalbe tubeless tyres, but I did need to use tyre levers - and the 'Easy Fit' montage fluid (aka soapy water) definitely made a difference too. I generally don't need levers for regular clinchers - in fact, in most cases, I don't find using levers makes the job any quicker or easier.

Being able to fit and remove tyres without levers and/or lubricants is definitely an advantage for roadside repairs.

So far, I've not done enough riding on the tubeless tyres to be able to form a meaningful opinion but I do wonder if the comfort advantages of lower pressures are perhaps offset by the stiffer sidewalls.
"The future's all yours, you lousy bicycles."

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: New tubeless convert... or so I thought
« Reply #79 on: 01 November, 2017, 01:39:27 pm »
http://www.cyclingweekly.com/videos/cycling-tech/tubeless-tyres-tested-destruction
this test only tells half a story, pin and nail holes are easiest to seal and they are rarely a cause for punctures in real world. cuts by small shards of glass and flints that damage the casing are most tricky to seal. inner tubes and tyre boots still need to be carried for random incidents, e.g. screw making a hole in both tyre and rim.



I reckon someone snuck up with a powerdriver in hand to put that one there
I've had a puncture very similar. It was a bolt, no pointed nose screw, which I spotted at the very last moment standing on end right in front of my front wheel as I was going down hill with following traffic. Front wheel rolls over it no problem but flicks it up and straight back into the very centre of my rear tyre. Oh how I laughed.
Riding a concrete path through the nebulous and chaotic future.

Re: New tubeless convert... or so I thought
« Reply #80 on: 01 November, 2017, 08:47:25 pm »
Why should tubeless tyres be so difficult to fit? Ok they might need a bit of assistance but I don't find the tubeless tyres on my baggage trailer particularly difficult to fit , no more than their tubed equivalents; and I can seat them without needing more pressure than I can get out of a bicycle footpump....

tubeless tyres need to seat more precisely on a bead seat in order to seal. Add a slightly stretchy tyre bead and it is virtually guaranteed that they will be a tighter fit. For some reason the well of a tubeless rim is usually shallower too, which makes the tyres difficult to fit.  Note those who proudly announce that 'they fitted brand X tubeless tyres without tyre levers'..... :o .... wtf..!!

The standard arrangement (in other applications than bicycles) is that a tubeless tyre is made nice and round, has a stiff bead, relatively stiff sidewalls, and a carefully moulded lip on the bead of the tyre. The net result of these things is that once the tyre is on the rim, it wants to seal and does so without great difficulty.

 Maybe your trailer tyres are more like that than they are like other current bicycle tyres, which are not nice and round, are not accurately sized, don't have stiff beads, don't have much in the way of a nice lip or stiff sidewalls.  IME current 'performance oriented' tubeless bicycle tyres don't fit and seal as well as other tubeless  tyres. Will they ever?  Well, probably not; the stiff sidewalls make for relatively high rolling resistance, which is tolerated in other applications but not so much in bicycles.

To put it in perspective, at ~50mph about 50% of the power that a car uses is expended against rolling resistance. The Crr values of good car tyres are not very good in bicycle terms (about x5 worse in round numbers I think). Car tyres are heavy, too; four car tyres (that support a car of 2000kg all up weight) weigh in the region of 50kg, i.e. 1/40th of the all-up weight of the vehicle is tyres. A typical value for a bicycle is in the region of 1/100th and racing bikes come in nearer 1/200th.  You might then take it as read that the experience with other types of tubeless tyre won't translate easily and directly to performance oriented bicycles.

cheers

Thanks for that explanation, makes perfect sense to me.

It still means to me that there is potential for progress to be made on ease of fitting. Bicycles generally have their tyres changed by their owners while car tyres are usually fittted by trained professionals in well equipped workshops (or am I being too naive?). Is there scope for looking at the type of tools used by off-road enduro motorcyclists and adapting/developing a bicycle equivalent? (The sort of tools that look a bit like car workshop tools in lighter, manual form)? I really don't think that bicycle tubeless is a fully developed article yet, more an immature technology.

Re: New tubeless convert... or so I thought
« Reply #81 on: 01 November, 2017, 10:16:01 pm »
I agree there is probably scope for all kinds of improvement yet.  I am mildly encouraged by Mavic's UST road standard but then again slightly discouraged that the well in the rims that meet this standard is so shallow; I expect this to make fitting any tyres more difficult that it need be otherwise.

 I really can't think why they have done this, unless they are concerned about tyres coming off the rim in use once they are flat or something.  Some folk think this is a big deal and have written extensively about it (for example see articles in the IHPVA archive).

 My experience is that once a beaded tyre is flat the bike is almost uncontrollable whether the tyre stays on the rim or not, but maybe others have experience/views on this?

 FWIW tubs are noticeably better in this respect; unless the tyre blows out mid-corner, I'd reckon your chances of stopping safely as being pretty good on the whole.

cheers

Re: New tubeless convert... or so I thought
« Reply #82 on: 01 November, 2017, 10:56:18 pm »
I suspect the shallower we'll makes it easier to inflate initially. The hardest rims I've dealt with were Pacenti TL28 mtb rims that needed several layers of tape, which also makes the head shelf less secure I think.

The Kinlin rims (22 and 31t) are fine with a single layer.

Security is generally thought important on tubeless. Even if they don't seal, they tend to deflate slowly giving time to slow and stop. Far preferable to a blow out at speed or in a corner where the tube opens up for a foot or more and lifts the tyre off the rim.

In terms of tape and the comment above on Gorilla tape - I think it's fine at mtb pressures, but less so at road. When you take the tyre off you'll find depressions in all the valve holes, waiting to become hanging chads...

Re: New tubeless convert... or so I thought
« Reply #83 on: 01 November, 2017, 10:58:36 pm »
And someone commented earlier on tubeless having stiff and uncertain mdortable sidewalls. I think that the faster tyres are all very nice to ride. Certainly I prefer Schwalbe Ones to tubed Ultremo. I still have a very soft spot for Vittoria Open Corsa and latex tubes though.

Re: New tubeless convert... or so I thought
« Reply #84 on: 01 November, 2017, 11:23:48 pm »
conversions are different but UST and other tubeless rims are meant to retain the tyre (in the event of deflation) by virtue of the lip in the shoulder of the rim.  If this works OK it seems to me that it doesn't really matter if the well is deep or not.

BTW it appears to be not well understood (in cycling circles at least) that the security of the tyre on the rim, and that the hooked bead had any tyre-retaining effect whatsoever, is entirely contingent upon where a tubeless tyre actually seals.

If the tyre has a lip at the bead edge that seals in the well of the rim, tyre pressure is pushing the bead into the hooked part of the rim, and the tyre is well retained.

If however the pressure seal is at the edge of the rim (and IME it can be with all kinds of tubeless tyres that are mounted on rims with imperfect wells) then there is no air pressure force pushing the tyre bead into the rim hook; the pressure is the same on both sides of the tyre bead.  Even with the thinnest tape, it seems likely that the tyre won't seal perfectly against the rim well where the tape finishes.

 If the bead lifts out of the rim well at all, once the tyre is fully inflated, the well seal will be lost and the tyre won't be well retained.

I suppose that this might explain why some tubeless bicycle setups are just not reliable; there have been quite a few reports of widish tyres at highish pressures just blowing off the rim without warning.

To combat this kind of thing even tighter fits of tyres (with remotely stretchy beads) on rims are required, and/or tyre beads that are much less stretchy.  There are moves afoot in this direction; dedicated tubeless bicycle tyres in many cases are getting heavier, with more rubber in the sidewalls, and more material to make a less stretchy tyre bead. 

Anyway none of this requires that the rim well be shallow, does it?  It does not appear to play a large role in sealing, or in (useful)  tyre retention once deflated; it arguably just makes the tyre difficult to get on and off the rim.

cheers

zigzag

  • unfuckwithable
Re: New tubeless convert... or so I thought
« Reply #85 on: 02 November, 2017, 12:08:57 pm »
<...>
Anyway none of this requires that the rim well be shallow, does it?  It does not appear to play a large role in sealing, or in (useful)  tyre retention once deflated; it arguably just makes the tyre difficult to get on and off the rim.

cheers

if the rim well is deeper on tubeless rim, it would be almost impossible to inflate the tyre as the air would be coming out underneath it. i didn't find particularly hard to mount tubeless tyres without levers (which are not recommended anyway). it's a bit trickier to unmount the tyres - there's an extra step to push the bead off the shelf which may or may not be hard, then use tyre levers to get the bead off the rim.

Re: New tubeless convert... or so I thought
« Reply #86 on: 02 November, 2017, 12:46:07 pm »
with other tubeless setups there is a deep well and the tyre still seals OK. The reason is that the tyre is constructed so that the beads spread themselves apart and make contact with the rim shoulder. Air pressure does the rest.

 Bicycle tyres don't spread themselves apart very well but I think there could be improvements here and a narrow deep rim well wouldn't cause big problems.

cheers

Re: New tubeless convert... or so I thought
« Reply #87 on: 02 November, 2017, 01:30:38 pm »
with other tubeless setups there is a deep well and the tyre still seals OK. The reason is that the tyre is constructed so that the beads spread themselves apart and make contact with the rim shoulder. Air pressure does the rest.

 Bicycle tyres don't spread themselves apart very well but I think there could be improvements here and a narrow deep rim well wouldn't cause big problems.

cheers

I suspect that using sidewalls that spring apart would lead to a less comfortable ride and greater hysteretic losses in the tyre wall when riding.

The few reports I've read of tyres coming off rims under pressure - wide tyres at relatively high pressure as Brucey says - seem to involve the use of tyres that are not intended for tubeless installation. These have much stretchier beads than tubeless type tyres, hence the failure mode.

I've seen it with a 32mm Vittoria Voyager Hyper set up tubeless at 80psi or just over. No sealant and the beads were still wet with soapy water. However, that's not an issue with road tubeless, just a consequence of attempting to use a tyre in a manner it wasn't designed for. I've also ridden said tyre tubeless at normal pressure (50 to 55psi in the back) with no apparent issues, but some nervousness and care. At least one report I read had a rear mounted 35mm Hyper blow off the rim of a fully laden touring bike during a long descent - I wonder whether heat generated by dragging the brake increased pressure and contributed? However, even here there is no issue with road tubeless as the tyre is not designed for that installation.


Back to Brucey's point about hooked rims, tubeless mtb wheels are increasingly using rims without hooks and, as he points out, hooks only really work where the seal is at the base of the bead or there is a tube in place.

Re: New tubeless convert... or so I thought
« Reply #88 on: 07 November, 2017, 07:22:01 pm »
Tonight's commute. Piss wet, cold, dark.

Thankful for tubeless tyres.

dim

Re: New tubeless convert... or so I thought
« Reply #89 on: 07 November, 2017, 08:15:02 pm »
1020 km so far (in one month) on my 2017 IRC Formula Pro RBCC tubeless road tyres and they still look brand new. I have not seen any rolling resistance data on these, but I would say that they roll as fast (if not faster) than Conti GP4000 SII but they grip a lot better and puncture resistance is very good (one puncture so far that sealed) ....

I do lots of miles and winter has just started .... I will buy them again when the current set needs replacing
“No great mind has ever existed without a touch of madness.” - Aristotle